THE MATERIALS FOR PRODUCING MAGNESITE are calcined powdered magnesite, chloride of magnesia, sulphate of magnesia, white sand, white talc and fine sawdust.
The magnesite should be kept in a container, proof against exposure to air and dampness, in order to preserve its full setting qualities.
Chloride of magnesia has the appearance of ice or alum and when exposed has the tendency to dissolve but does not deteriorate. It is the chemical which when united with the magnesite produces the binding or cement qualities.
Sulphate of magnesia or epsom salts is an easily secured material and is used in very small quantities in the formulae for producing magnesite cement and which is given later in this chapter.
The white talc or soapstone used for giving a smooth and polished white background is used as a filler.
White sand and the fine sawdust should be absolutely clean and are mixed with the other ingredients to produce the composite mixture to produce Magnesite Cement.
TO COMBINE THE INGREDIENTS proceed as follows:
FIRST MIXTURE. Two and one-half pounds of powdered magnesite and one pound of white talc are mixed thoroughly with one quart of fine sawdust. To this mineral, dry color similar to that used and described for color cement should be added if a color tone is desired. About one-half as much color should be used as there is magnesite. In other words, one pound of color should be used with two and a half pounds of powdered magnesite. A stone mortar should be used to grind the entire mixture well together.
This first combination is a dry mixture and is then mixed with the second mixture which is liquid.
SECOND MIXTURE. Take five parts by weight of chloride of magnesia solution with a density of 25 tested with a Baumé hydrometer which is a simple glass tube secured at any druggist for registering solutions. To the chloride of magnesia solution add one-half part by weight of sulphate of magnesia which is epsom salts and test with the hydrometer until it records 15.